Gomphotaria pugnax, a new genus and species of Late Miocene dusignathine otariid pinniped (Mammalia: Carnivora) from California

16 Pages·1991·13 MB·English

by  Lawrence G Barnes

,
Gomphotaria pugnax a New Genus and
Species of Late Miocene Dusignathine
Otariid Pinniped (Mammalia: Carnivora)
from California
Lawrence G. Barnes1 and Rodney E. Raschke2
ABSTRACT. The nearly complete skeleton ofGomphotariapugnax a newgenus and species ofgiant
,
fossilpinniped, has been discovered in the latest Miocene (ca. 5 to 8.5 million years) marineCapistrano
Formation insouthernCalifornia,U.S.A.This remarkablepinnipedisassignableto theotariidsubfamily
Dusignathinae and is convergent with true walruses of the subfamily Odobeninae by possessing large
uppercanine tusks but is unlike odobenines in othercranial and postcranial osteological features. Both
upperand lowercaninesare enlarged,procumbent,and worn anteriorly,indicatingthat theanimal may
haveprobedthesubstrateinsearchofbenthicinvertebratesforfood. Extremebreakageandsubsequent
wearofthelarge,single-rootedcheekteethindicatethatatleastsome,ifnotallofthefoodspecies(e.g.,
mollusks)probablyhadhardshells.Absenceofahighlyvaultedpalate,presentinwalruses,indicatesthat
G. pugnax did not suck bivalve innertissues from the shells using the tongue-piston method employed
by walruses. Although G. pugnax is distinguishable from type and referred specimens ofall previously
described odobenines and dusignathines, the continuing problem of disparate materials continues to
plague interpretation of the group, and there are as yet unresolved problems of synonymies among
previouslydescribed taxa.
INTRODUCTION penning (1975, 1976), Repenning and Tedford
(1977),Tedford (1976), Barnes (1979, 1987, 1989),
This is a preliminary report of a new genus and Barnes,Domning,and Ray(1985),andWozencraft
speciesofgiantfossilpinnipedfromtheCapistrano (1989a, b). These authors have proposed several
Formation in Orange County, southern California schemesofclassificationforthesealions,furseals,
(seealsoBarnesandRaschke, 1989).Thefossilwas walruses,andtheirextinctrelatives.Asaresult,the
excavatedfromthelatestMiocene(5to8.5million classificationofthegroupiscurrentlycontroversial
years (Ma)) part of the siltstone facies of the Cap- (seeBarnes, 1987;Barnes,Domning,andRay1985:
issetqruaennocFeoromfatMiioonc.eTnheisafnodrmPaltiioocnenisepamratroifneatsheidcik- a36n,d3W8,ystsabl(e1918)9,)ahnadveWyesvsen(1a9r8g7u)eadndthaBterwtaal,rRuasye,s
mentary rocks in the southeastern part of the Los are closely related to the phocid seals.
Angeles Basin that has produced important and We classify the new taxon described here in the
abundant fossil marine vertebrates. The fossil was extinct otariid subfamily Dusignathinae of Mitch-
dthiescPoavceirfiecdOicnetahne,hiinll1y9a8r0e,aboyfpSaalneoCntloelmoegnitset,swnehaor Deluls,i1g9n6a8t.hiPnraieorwtaosthmeonporteysepnitc,stDuduys,igthneatshuubsfasmainl-y
were salvaging fossils during construction-related tacruzensis Kellogg, 1927, beingthe onlyincluded
grading. species.The holotypeofD. santacruzensisis from
Inrecentyears,ourknowledge ofthe evolution- the latest Miocenepart ofthe Purisima Formation
ary history of sea lions, fur seals, and walruses in nearSanta Cruz in central California,and that for-
gtrheeatlfya.miTlhyeOftoasrsiilidraeeco(rsdenhsaus lhaatdo)ahmaasjoirncirmepaascetd misattriaonno FisorbmroaatdiloyncoofrrseloauttihveerninCaagleifwoirtnihat(hReeCpaepn--
on interpretations of otariid phylogeny as is evi- ning and Tedford, 1977:4, 43-44; Barnes, 1976:
denced in reviews by Mitchell (1968, 1975), Re-
331, table 5, 1985:18).
Kellogg(1927)hadconsideredD. santacruzensis
1. Curator and Section Head, Section of Vertebrate to beasealion,although he recognizedthatithad
Paleontology, Natural History Museum of Los Angeles characters of both sea lions and walruses. When
County, 900 Exposition Boulevard, Los Angeles, Cali- Mitchell (1968:1894-1895) diagnosed the subfam-
fornia 90007. ily Dusignathinae, he listed characters thatshowed
2. Instructor,CaliforniaAcademyofMathematicsand thetaxonto beintermediatebetweensealionsand
Science, California State University at Dominguez Hills,
Carson,California90747;andMuseumAssociate,Section walruses,anditoccupiedthisintermediateposition
ofVertebratePaleontology,NaturalHistoryMuseumof in his phylogeny (Mitchell, 1968:fig. 16). Mitchell
LosAngelesCounty,900ExpositionBoulevard,LosAn- later suggested (1975:18) a somewhat different re-
geles,California 90007. lationship when he indicated that he considered
Contributionsin Science,Number426, pp. 1-16
Natural History Museum of Los Angeles County, 1991
Dusignathus Kellogg, 1927, to be more closelyre- SYSTEMATICS
lated to the Desmatophocinae than to the Otari- Class Mammalia Linnaeus, 1758
inae.RepenningandTedford(1977),however,con-
sidered Dusignathus to be a member of the Order Carnivora Bowdich, 1821
subfamily Imagotariinae Mitchell, 1968 (Imagotari- Family Otariidae Gill, 1866
inae being a senior synonym of Dusignathinae on Subfamily Dusignathinae
the basis of page priority) and classified it within Mitchell, 1968
the family Odobenidae (walruses).
The importanceofthenew fossil described here TYPE GENUS. Dusignathus Kellogg, 1927.
isthatitrecords,forthefirsttimeinadusignathine, INCLUDED GENERA. Dusignathus Kellogg,
definitely associated cranial and forelimb bones, 1927; and Gomphotaria, new genus.
elements of critical importance in pinniped system-
atics. This information will be pivotal to the de- Gomphotaria, new genus
scription and understanding of other taxa repre-
sented by disparate and less complete parts. DIAGNOSIS OF GENUS. A genus of Dusigna-
Therefore, description of the taxon now is timely thinae differing from Dusignathus by having cra-
and will facilitate research on othertaxa and spec- nium with high sagittal crest, rostrum laterally ex-
imens. The new taxon also documents previously pandeddistallytoaccommodatetusks,postglenoid
unknown diversity in the Dusignathinae. We de- processofsquamosalrelativelylarger,mastoid-par-
scribe the cranium, dentaries, and some forelimb occipital crest more compressed anteroposteriorly
bones because they serve to differentiate the new and expanded dorsoventrally, relatively largerhor-
taxon from all previously described large otariid izontal shelf projecting laterally over external
pinnipeds of similar age. We intend to prepare a acoustic meatus, external aperture ofstylomastoid
subsequent paper illustrating and describing in de- foramen directed anterolaterally rather than ven-
tail cranial variability and postcranial osteology of trolaterally; by having dentary relatively shallower
the new taxon based on the holotype and other dorsoventrally and relatively thicker transversely,
specimens;however,thatworkisbeyondthescope with more recumbent coronoid process, more
of this study. prominentlaterallyprojectingangleofdentary,rel-
atively largerand more rugose symphyseal surface,
pterygoid process tabular and directed medially
rather than posteromedially, and lesser degree of
METHODS AND MATERIALS angular divergence from mandibular symphysis at
midline (indicatinglongerand narrowerskull); and
Theclassificationusedinthisstudyisderivedfrom those by having upper and lower canines much larger,
ofMitchell (1968)and Barnes (1979, 1989) inwhich En- developed as tusks, more procumbent, and having
aliarctinae, Otariinae, Desmatophocinae, Allodesminae, fluted roots covered with thick cementum and ex-
Imagotariinae, Dusignathinae, and Odobeninae are rec-
posed outside of alveoli, cheek teeth with crowns
ognized as separate subfamilies within the family Otari-
idae, sensu lato. The subfamily Dusignathinae is recog- more bulbous,and upperand lowerPI more shal-
nized here based on characters listed by Mitchell (1968: lowly rooted.
1894-1895)andonadditionalcharacters.Werestrictour TYPE AND ONLY INCLUDED SPECIES.
characterization and comparisons of D. santacruzensis Gomphotariapugnax,newspecies,latestMiocene,
to its holotype because referral of postcranial bones to California.
thespeciesistenuous.Geochronologicagesoffossilpin- ETYMOLOGY. DerivedfromGreek;gomphos,
nipedscitedhereinaremodifiedfrom thosegiven byRe- for peg, nail, or bolt; in reference to the simple,
penningandTedford(1977)and Barnes(1979) following round-rooted,peglikecheekteethofthispinniped;
the revised radiometric time scale ofDalrymple (1979).
Cranial measurementsin Table 1 thatwere definedby plus otaria, a root derived from the generic name
Sivertsen (1954:18-20) are identified by his numbers in of the South American sea lion, the type genus of
brackets. Other measurements are as defined by Barnes the family Otariidae, in reference to the otariid
(1972:fig. 1, 1979:4-5). The anatomical terminology, in- affinities of this taxon.
cluding dental nomenclature, used here is adapted from
that of Howell (1928), Miller, Christensen, and Evans Gomphotaria pugnax, new species
(1964),Mitchell(1966,1968),MitchellandTedford(1973),
Barnes (1972, 1979, 1989), and Repenning and Tedford Figures 1, 2, 3a
w(1i9t7h7)a.Tsuhbelibmoanteesosfhaowmnmoinnithuemilclhulsotrraitdieontsowemraekecotahteeidr DIAGNOSIS OF SPECIES. The genus is pres-
features more visible. ently monotypic and the generic diagnosis serves
Acronyms used forinstitutions are: for the species.
LACM—NaturalHistoryMuseumofLosAngelesCoun- HOLOTYPE.LACM121508,virtuallycomplete
UCtyM,PLo—sUAnnigveelressi,tyCaolfifCoarlniifao.rnia Museum of Paleontol- rsikeesl,ectoolnl,ecitnecdlu2d1inAgugcursatni1u9m,80lebfyt La.nGd.rBiagrhntesd,enEtda--
ogy, Berkeley, California. ward D. Mitchell, Marilyn M. Morgan, Rodney E.
USNM—National Museum of Natural History, Smith- Raschke, and Mark A. Roeder.
sonian Institution,Washington, D.C. TYPELOCALITY. LACM4631,SanClemente,
2 Contributions in Science, Number 426 Barnes and Raschke: New Miocene Pinniped
Orange County, California. The holotype was ex- Table 1. Measurements (in mm) of the holotype cra-
cavatedapproximately70mnorthofHighway 101 nium of Gomphotaria pugnax, new genus and species,
at 10 to 12 m depth in a hill in the SW*/4, SWV4, LACM 121508. SeeMethodsandMaterialsformethods
Steocp.og2r8,apTh.ic8quS.a,drRa.ng7lWe,.,USSGaSn,C1l9e6m8e,nt1e:2,4C,a0l0i0fsocranliea, odifcmaeteastuhraetmietnwtass.Peasrteinmtahteesdebsyardoouunbdliangmeaashaulrfemwiedntth.in-
at approximately 33°26'26" north latitude, and Length aspreserved (rostral tip to dorsal
117°37'20" west longitude. margin offoramen magnum) 466.0
FORMATION AND AGE. Siltstone facies of Length oftooth row, C to M1 177.0
the upperpart of the Capistrano Formation, latest Width ofrostrum across canines (12) (164)
Miocene,ca. 5 to 8.5 Ma, correlativewith most of Width ofrostrum across base ofI3 (65)
the Hemphillian North American Land Mammal Width ofpalateacrossalveoli ofP4 (114)
Age. Width across antorbitalprocesses (5) 139.5
The Capistrano Formation, a laterally extensive Width acrossgreatest intertemporal
marine sedimentary rock unit in southern Orange constriction 45.0
County,includesstrataoflatestMioceneand early Width of braincase at anterioredge of
Pliocene age, consists mostly of silty shales in- glenoid fossa (8) (100)
terbeddedwithdiatomitesandsandstones,andrests Zygomatic width (17) (280)
conformablyontheMiddleandLateMiocenema- Auditorywidth (19) (230)
rine Monterey Formation (Edgington, 1974). This Mastoid width (20) (250)
formation was deposited in the extreme south- Greatestwidth ofanteriornares 50.9
easternpartofthestructuralanddepositionalbasin Greatest height ofanteriornares 56.2
known as the Los Angeles Basin. The siltstone fa- Width ofzygomatic root ofmaxilla (14) 38.5
cies of the Capistrano Formation, described by Transverse diameterofinfraorbital
Woodford (1925) for exposures in the San Juan foramen 27.6
CapistranoareaofOrangeCounty,consistsofolive Anteroposteriordiameterright I3 alveolus 33.3
brown to gray (when weathered) and dark brown Anteroposteriordiameterright canine
to black (when fresh), sandy siltstone, with in- alveolus 68.8
terbedded sandstones and diatomaceous shales. Anteroposteriordiameterright P1 alveolus 21.2
There are localized occurrences of breccia at the Anteroposteriordiameterright P2alveolus 20.6
baseofthisformation.Thesiltstonememberisthe Anteroposteriordiameterright P3 alveolus 19.8
deepwater,offshore(distal)faciesoftheCapistrano Anteroposteriordiameterright P4alveolus 16.5
Formation, and is laterally equivalent to, and in- Anteroposteriordiameterright M1 alveolus 20.3
terfingers with, the nearshore (proximal) facies of
theCapistrano Formation, known as the Oso Sand
Member(Vedder, 1972),which hasyielded horses,
rabbits, and other fossils of Hemphillian age. Al-
though the published vertebrate paleontological completelypreserved, but when it was exposed by
record of the Capistrano Formation appears to be earth-moving machinery, much of the ventral sur-
meager(Barnes,1976;Barnes,Raschke,andBrown, facewasscrapedaway. Becauseofthis,theleftside
1984,1987),manyfossilshavebeenrecoveredfrom andposteriorpart ofthepalate, the left zygomatic
therock unitand awaitdescription. Theage ofthe arch, and most ofthe basicranium are missing. Re-
rock unit has been determined partly on the basis maining parts of the cranium are preserved in ex-
ofitsstratigraphicand structuralrelationshipswith cellent condition.
other rock units of known age and partly on the The individual represented by the holotype was
basis of published and unpublished fossils. The an old adult male (Group I of Sivertsen (1954)) on
Capistrano Formation is broadly correlative with the basis of the following observations: (1) of the
the lower part of the Almejas Formation on Isla ninecranialsuturesthatSivertsenconsidereduseful
Cedros,BajaCalifornia,andwiththePurisimaFor- for age determination, eight are closed and fused,
mation near Santa Cruz in central California (Re- six are obliterated, only the anterior part of the
penningandTedford,1977:4,43-44;Barnes,1976: interfrontal suture and the posterior part of the
331, table 5, 1984, 1985:18). premaxillary-maxillary suture are still visible, and
ETYMOLOGY. Derived from Latin; pugnax, the basioccipito-basisphenoid suture is presumed
for combative or contentious; in reference to the to have beenfusedand obliterated;(2) thecranium
probableappearanceinlifeofthisgiant,adult,male yields a suture age of at least 34 (see Table 2) by
individual with procumbent anterior teeth, large employing the methodology of Sivertsen (1954),
extremely worn cheek teeth, and a high forehead. thus placing it in the old range for the adult age
DESCRIPTION AND COMPARISONS. Cra- class;(3)asinRecentadultmaleotariinesandmany
nium.Thecranium(Fig. 1,Table 1)ismassive,with fossil otariids, a sagittal crest is present; (4) the ca-
large procumbent canines, stout zygomatic arches, nines are fullyerupted and heavilyworn; (5) bones
relatively small orbits (for a pinniped), a relatively throughout the skeleton have extreme develop-
small braincase, a thick nuchal crest, and a high mentofcrests,rugosities,processes,and othersec-
sagittalcrest.Apparentlythecraniumwasoriginally ondary age and male sex characters; and (6) a bac-
Contributions in Science, Number426 Barnes and Raschke: New MiocenePinniped 3
Figure 1. Gomphotaria pugnax, new genus and species, holotype cranium, LACM 121508, from LACM locality
4631; a, dorsal view; b, right lateral view; c,ventral view.
ulum is present. We have given the basioccipito- togeny,and itdefinitelyfusespriorto fusionofthe
basisphenoid suture a score of 4 in Table 2, indi- basisphenoid-presphenoid suture, and this latter
catingour beliefthatitwas closedand obliterated, suture is fused in the holotype. The exceptionally
even though it is not preserved on the specimen. high sagittal crest is rivaled only by that of Recent
This suture is one of the first to fuse during on- California sea lions (Zalophus californianus (Les-
1
4 Contributions in Science, Number 426 Barnes and Raschke: New MiocenePinniped
son, 1828)) in which the crest is a diagnostic male Table 2. Degree ofclosure of sutures of holotype cra-
sofecmoonsdtarfyosssielxacnhdarlaivcitnegrot(aOrriridesthaalv.,e1a9t7l0e)a.stMsaolmees LniAuCmMof1G2o15m0p8h.otaSurtiuarepungonmaexn,clnaetwurgee,nunsumabnedrss,pecaiensd,
developmentofacrest,butsagittalcrestsareabsent methodsfollow Sivertsen (1954).
in odobenine walruses. Degree
The rostrum is large and expands distally (Fig. Suture of
la) around the roots of the large upper canines. number Suture name closure
The anterior narial opening is shaped as an elon-
gated oval and is bordered by rounded margins of I. Occipito-parietal 4
thepremaxillae. Immediatelyanteriorto the narial II. Squamoso-parietal 4
opening,thepremaxillaeprotrudetoformaprom- III. Interparietal 4
IV. Interfrontal 3
inent, slightly up-turned tuberosity. Such a tuber-
V. Coronal 4
osity is primitively present in various otariid pin-
nipeds, especially members of the Otariinae and VI. Basioccipito-basisphenoid 4?
Imagotariinae.Thereisnoprominentprenarialshelf VII. Maxillary 4
asinspeciesofAllodesmus(Mitchell,1966;Barnes, VIII. Basisphenoid-presphenoid 4
1972). The convex cheek region of the maxilla IX. Premaxillary-maxillary 3
around the canine root is very rugose and perfo- Total (sutureage) 34
rated by many small foramina. Most parts of the
sutures between the premaxillae and maxillae are
obliterated by fusion. An exception to this is the
partofthesuturethatisadjacenttothenasalbones. dorsolateral to each condyle and extends outward
The ascending (posterior) process of each maxilla to the nuchal crest. The exoccipitals flare broadly
extends posteriorly for approximately one-half of andaresomewhatconcaveposteriortothemastoid
the length of the nasals (Fig. la). The nasal bones processes. There is no indication of a large, pos-
are elongated and, as in Allodesminae, taper pos- teroventrally projecting paroccipital process, such
teriorly to form wedges between the anteriorpro- as occurs primitively in enaliarctine, desmatopho-
cesses of the frontals. Rather than having trans- cine,andallodesmineotariids(Barnes,1979, 1989).
versely flat anterior terminations as in most The orbit (Fig. lb) is small compared to most
Otariidae, the anterior ends of the nasals of G. fossil and Recent pinnipeds, being approximately
mm
pugnaxareoblique,withretractedmedialmargins, 68 in diameter. In anterior view, the aperture
so that they are separated to form a small gap be- of the large infraorbital foramen is roughly trian-
tween them anteriorly. gular. The dorsal branch of the jugal is centered
The anteriorprocesses ofthe frontals areprom- aboveit(primitivecondition),beingneitherretract-
inent and, unlike the condition in other known edtowardtheorbitasinAllodesminae(seeBarnes,
kinds ofotariid pinnipeds,are elevatedand lapan- 1972),norflaredoutanteriorlyovertheinfraorbital
teriorly over the posterior ends of the nasals and foramenas in Otariinae. The ventral branch ofthe
maxillae. Each frontal process is confluent with a jugal ascends from the level of the cheek tooth
prominent antorbital process. Immediately poste- row, and does not depart from the snout at the
riorto the nasals,the frontalsare cleft medially by levelofthecheektoothalveoliasinAllodesminae.
a shallow sulcus marking the interfrontal suture. The zygomatic part of the jugal is upturned into a
Thefrontalsareelevatedandjoinwiththeparietals small, thickpostorbitalprocess,which hasarather
overthe intertemporal region and the braincase to sharp, crestlike posterior margin. Ventral to the
form a highly elevated and arched sagittal crest orbit, the jugal is thick, and is exceptionally deep
(derived character). This crest is irregular and rel- where it curves posteroventrally ventral to the zy-
ativelyrugose,indicatingprominenttemporalmus- gomatic process of the squamosal and slightly un-
cleattachments,andhasafinemediangroovemark- derhangs the anterolateral corner of the glenoid
ingthecourseoftheobliteratedinterparietalsuture. fossa (Fig. lb, c).
Overthe intertemporal region,the sagittal crestta- A broad, anteroposteriorly elongate squamosal
persventrolaterallytotheorbitalmargin,however, fossa separates the zygomatic process of the squa-
posteriorlyitsverticalsidesdescendabruptlytothe mosal from the lateral wall of the braincase. This
surfaceofthebraincase.Posteriorlythesagittalcrest fossa is continuous laterallywith averyprominent
is confluent with the right and left parts of the shelf that projects laterally dorsal to the external
nuchalcrest,thatflareposteriorlyoverand beyond acoustic meatus. This shelf extends between the
theoccipitalshieldandcurveanterolaterallytojoin zygomatic process of the squamosal and the ver-
the dorsal surface of the mastoid processes. Small tically expanded, rectangularly shaped, combined
scattered foramina pierce the irregular surface of mastoid and paroccipital process. The zygomatic
the braincase. process ofthe squamosal flares anterolaterallyand
The occipital shield is high and broad. A prom- archesanterodorsally,becomingabruptlyveryslen-
inent, median, vertical crest on the supraoccipital der in its anteriorpart dorsal to the jugal.
extends from immediately dorsal to the foramen The right bonyorbitalwallisvirtuallycomplete,
magnum to the nuchal crest. A convex area lies although the bone surface has many small cracks.
Contributionsin Science,Number426 Barnes and Raschke: New MiocenePinniped 5
There appears to have been a moderate-sized, from the alveolus and we estimate that in life it
somewhatbilobedorbitalvacuityapproximatelyin extendedmorethan 150mm from thealveolus.At
the middle of the orbital wall. The lacrimal fora- the alveolarmargin, the canine root measures 69.5
menhas beenlost(derivedcharacter).Directlypos- mm anteroposteriorly by 49 mm transversely. The
terior to the orbital aperture of the infraorbital crown ofthe canine tapersand curves slightlyven-
foramenisasmallsphenopalatineforamen.Within trally and medially.
theposteriorpartoftheorbit,theopposingorbital The row of five cheek tooth alveoli on either
wallsare closelyappressed,somewhatasinderived side ofthepalate is oblique to the sagittalplane in
species of Otariinae, and not widely separated as the mouth, extendingfrom the posteromedial side
in the Recent walrus Odobenus rosmarus (Lin- of the canine to the lateral side of the palate near
(
naeus, 1758)). Because of this, the optic foramina thebaseofthezygomaticarch.Themaxillaextends
of G. pugnax are relatively close together. They ventrally along the labial border of the alveolar
are located lower on the cranium than in typical row, with pointed projections separating the alve-
Otariinae, but more dorsally than in O. rosmarus. oli. The alveoli are for five cheek teeth identified
M
The relatively small orbital fissure is ventrolateral as P1-4 and 1. They are slightly procumbent and
to the optic foramen, separated from it by a strut crowded, so that interalveolar septa are thin or
ooffbtohnee,ptaenrdyglooicdattehdatimfmoerdmisattehleydloatresraalltmoatrhgeisntrouft aabnsaelnvte.oTlhuseampipdrdolxeimtaotoethl,yP333,mismdeedpeleyp.roTohteeda,lvweiotlhi
the palate. of the more anterior and posterior teeth are less
The palate (Fig. lc) is elongated and its entire deepM. The alveoli of P1-4 are circular, whereas that
surface is perforated by numerous tiny foramina. for 1 is bilobed. The alveolus for P1 is very shal-
Relativelysmall,paired, incisive foraminaarepres- low (ca. 10 mm). In fact, owing to its proximityto
ent at the anterior end. The cheek tooth rows di- the root ofthe canine tusk, it could not have been
verge slightly posteriorly, and between them the much deeper. The alveolus for P2 is approximately
mm
cmheadriacatnerp)a.rtThoifstvhaeuplatliantgeiissdsilfifgehrtelnytvfarulotmedth(adterinivOe.d 2320mm ddeeeepp.,Tahnedsthhaaltloowf,tbhieloPb4edisalavpeporlouxsimfoarteMly1
rosmarus, because the vaulted portion is narrow indicates that the root of that tooth had a vestige
and anteroposteriorlyelongated, and easily half of of the double-rooted condition (primitive).
the apparent vaulting results from the addition of Because of the extensive damage to the basi-
rugose bony tissue along the lingual side of the cranium (Fig. lc), onlypart of the right squamosal
cheek tooth alveoli. Between the P3’s are a pair of and earregion can be described. Theglenoidfossa
prominent palatine foramina, in the same location is broad with rounded edges and with a ventrally
as in species of Enaliarctinae (see Barnes, 1979, deflected anterolateral corner. The external acous-
1989), and these foramina are likewise continuous ticmeatusisanteroposteriorlycompressedbetween
with anteriorly directed sulci (primitive character). the postglenoid and mastoid processes (derived
Thesesulcidemarcatethemedialedgeoftheabove- condition), and a space of only approximately 15
mentionedareasofrugosebonemedialtothecheek mm separates the two processes. The entrance to
tooth alveoli. Unlike the homologous palatine fo- the external acoustic meatus is therefore narrow
ramina in enaliarctinces, which are directed ante- and high, in contrast with the situation in Imago-
riorly, these are nearly vertically oriented (derived tanadownsiMitchell,1968,forexample,inwhich
character).Theinfraorbitalplateofthemaxillahas the entrance to the meatus is broad and low, even
a thick, rounded border extending posteriorly to thoughtheinframeatallipiswrinkledfromantero-
the pterygoid region, and there is only a vestigial posterior compression. The dorsal surface of the
pterygoidprocessnearthe maxilla-palatinesuture. externalacousticmeatusofG.pugnaxisperforated
Thereare no alveoli forI1-2, teeth that areprim- by several small holes, not usuallypresentin otari-
itivelypresentin mostspecies ofotariids,and in G. ids,andthesemaybetheresultofsomepathology.
pugnax the place that such teeth occupy in other The inframeatal lip bears a small foramen 2.5 mm
pinnipeds is merely a rugose pad of bone (derived in diameter. The aperture of the stylomastoid fo-
character).ThetwoverylargeI3’swerepresent;the ramen is large and, as in I. downsi and Pontolis
alveolus for left I3 is crushed, but the uncrushed, magnus (True, 1905a), is directed anterolaterally
procumbent, right one is oval in cross section and toward the inframeatal lip.
measures approximately 22.5 mm transversely by The tympanic bulla is mostly broken away to
33.3 mm anteroposteriorly. The canine, developed reveal a natural internal cast of siltstone. We left
into atusk, isalsoveryprocumbentandverylarge. this matrix cast intact because it is our only indi-
Althoughtheapexofthecrown oftherightcanine cation of the former size and shape of the bulla.
was badly broken by earth-moving machinery, The entire bulla was positioned posteromedial to
enough remains to show that it suffered extreme the glenoid fossa, in the primitive carnivoran and
abrasionduringlife.Thereisnotraceofanyenamel otariidcondition.Thematrixcastindicatesthatthe
remaining on it. The root is deeply fluted by alter- tympaniccavitywaslargeandnearlyspherical,with
natinglongitudinalgroovesandridges,andhasthick a somewhat flattened medial side. Its size indicates
deposits of cementum. To the point of breakage, that the ventral surface of the bulla descended to
mm
the right canine of the holotype extends 135 apointventraltothepostglenoidandmastoidpro-
6 Contributions in Science,Number 426 Barnes and Raschke: New MiocenePinniped
,
Oc 10
Figure2. Gomphotariapugnax,newgenusandspecies,holotyperightdentary,LACM 121508,fromLACMlocality
4631;a, lateralview; b, occlusal view; c, medial view.
cesses. This condition is unlike that of the ima- riorly and posteriorly. Unlike the condition in D.
gotariine P. magnus, in which the bulla is flat and santacruzensis, there is no genial tuberosity in G.
does not project ventral to the surrounding pro- pugnax.Themandibularsymphysis(Fig.2c)ismore
cesses. oval than rhomboidal in shape, unfused, and very
Dentary. The holotype ofG. pugnax includes a rugose.A largefossaispresentjustposteriorto the
completerightdentaryandan incompleteleftden- ventral edge of the symphysis. The dorsal margins
tary(Fig. 2,Table 3). The horizontal ramus is deep ofbothdentarieshaverugose,pittedexostosesalong
dorsoventrally, like that of Dusignathus santa- thetoothrows.Thecoronoidprocessascendsgrad-
tchriuczkeensstisp,obrutitoinsamtutchhetahnitcekreirortreannds.veTrhseelyb,owniethsuirt-s Tuahlelymfarsosmettehreicalvfeooslsaarirsodweaenpdainsdloewlaonngdartoeudnd(Feidg..
face is very rugose and pitted. A sulcus along the 2fao)s,saunilsidkeeetphabtutofsoDm.eswahnatatcsrquuzaernes.isThien cwohnidcyhlethies
ventrolateralmarginoftheramusextendsfromthe largewithalaterallydirectedshelflikestrut.Alarge,
posterior margin of the symphysis to just anterior medially directed pterygoid process is present.
totheangle(Fig.2a). On thelateralsurfaceofeach Therearenoalveoliforlowerincisors,norspace
dentary are four mental foramina; two large, cen- for them, between the two enlarged canines. The
trally located foramina, and a smaller both ante- lowercaninesare large,procumbenttusks, smaller
Contributions in Science,Number426 Barnes and Raschke: New MiocenePinniped 7
Table 3.—Measurements (in mm) of dentaries of Gomphotaria pugnax, new genus and species, holotype, LACM
121508. indicatesa measurement was not possible.
Right Left
Total length 410.0 378.0
Length alveolarrow, C-M! 182.0 170.0
Length ofsymphysis 140.5 142.0
Breadth ofsymphysis 92.5 86.0
Depth oframus at P3 100.0 9—1.0
Anteroposteriordiameteralveolus C 5—9.4
Anteroposteriordiameteralveolus P 19.3
t
Anteroposteriordiameteralveolus P 21.8 20.2
2
Anteroposteriordiameteralveolus P 21.9 21.8
3
Anteroposteriordiameteralveolus P4 21.6 2—3.2
Anteroposteriordiameteralveolus M, 15.8
than the upper tusks, oval in cross section, with TheleftP4alveolusisapproximately28mmdeep,
prominent fluting below the crown. The apex of and the right P4isalso inplace inthe dentary. This
the right canine is intact and is heavily worn. Two tooth resembles the P3, and also has a faint longi-
patches of thin, smooth enamel remain; one lat- tudinallabialsulcusonitsroot(Fig.2a).Thecrown
erally and one posteromedially. A large oblique issimilarlywornoff,butsufficientpartsofitremain
wearsurface on theposterolateral side is from oc- to show that there is a relatively prominent,
clusion with the upper canine. A wear surface on smoothly rounded lingual cingulum. The right al-
themedialsideundoubtedlyresultsfromocclusion veolus for Mj is approximately 20 mm deep and
with the large I3. The anterior face of the crown indicates that the root ofthis toothwas circularin
also shows extreme wear, caused not by occlusion cross section.
with any other tooth but by external abrasion. Forelimb. Association ofthe rightforelimbwith
The lower postcanine dentition consists of Pj_4 the holotype is critical because the bones serve to
and Mj. The lower cheek tooth row is oriented differentiate this species from at least two other
slightly obliquely to the axis of the horizontal ra- walrus-likefossiltaxathatarenotknown bycrania
mus. Oppositeto thesituationwith the upperrow, or mandibles (see comparisons in Discussion). The
itextendsfromtheposterolabialside ofthe canine humerus of the holotype is fused pathologicallyat
to the lingual side of the dentary posteriorly (Fig. the elbow joint with the radius and ulna (Fig. 3a).
2b). On each dentary of the holotype, one tooth Thisfusionisofunknowncause,butisanarthrosis
was lost by accident or pathology and its alveolus inthegeneralsense. Exostosesatthejointaremas-
had become filled with a secondary bony growth. sive;however,thediagnosticcharactersofthebones
On the right dentary, the P had been lost and, on are clearly visible.
x
the left, it was the Mj. Unlike the procumbent The humerus is relatively elongated, with an
upper cheek teeth, the lower cheek tooth alveoli elongated, anteriorly directed deltoid crest. As in
arevertically oriented,and theposteriorones even species of Otariinae and Allodesmus, the deltoid
slope slightly posteriorly. All of the alveoli (and cresthasanearlystraightanteriorborder,andcurves
roots) of the lower cheek teeth are nearly round. rather abruptly to the shaft of the bone distally.
The largest and most deeply rooted, as with the Theheadofthehumerusisrelativelylarge,andthe
uppers, are in the middle of the row, with the Pj greatertuberosityextendsproximallybeyondit.As
and M, being the smallest. The cheek teeth are in walruses in general and in Valenictus imperi-
crowded, progressively closer posteriorly, so that alensis Mitchell, 1961, the deltoid tuberosity is on
there is virtMually no interalveolar septum between the lateral side of the deltoid crest.
the P4 and t. Theradius isrelativelyshortandstout,although
There is a large (15 mm) diastema between the less so than the radius belonging to the forelimb
posteriormarginofthecaninealveolusandP,.The of an unidentified walrus-like pinniped that was
left Pj alveolus is approximately 11 mm deep. The reportedbyMitchell(1962)fromthePurisimaFor-
aPl2veaollvueosliis a3r7e.52m4manddee2p8, amndmthdeeerpi.ghtThtoeotlheftisPin3 hmaastiloinmabtSbaonnteasCrtuhazt.Tahriesmsopreecimmeanss(ivLeACthMan30a1n1y)
place in the dentary. The root of the right P has pinnipedyetdescribed,withthepossibleexception
3
thick cementum and a longitudinal groove on the of the aberrant walrus-like V. imperialensis. The
labial side (Fig. 2a), a vestige of an earlier, more forelimb from Santa Cruz was identified as a pos-
primitive,two-rootedcondition.Thecrownofthis siblenewgenusandspeciesofodobenid byMitch-
tooth is almost entirely worn off, but enough re- ell (1962) and was tentatively assigned to D. san-
mainstoindicatethatitwascircularincrosssection tacruzensis by him (Mitchell, 1975:19) and by
and had smooth, thin enamel. RepenningandTedford (1977). Lackingassociated
8 Contributions in Science,Number 426 Barnes and Raschke: New MiocenePinniped
Figure3. Forelimbbonesoffossilpinnipeds;a,Gomphotariapugnax,newgenusandspecies,holotype,righthumerus,
radius, and ulna, pathologically fused at the elbow joint, LACM 121508, from LACM locality 4631, lateral view; b
andc,PliopediapacificaKellogg, 1921,holotype—,USNM 13627;b,distalendoflefthumerus,lateralview;c,proximal
part ofleftulna, lateral view; to different scales scale barforaat upperleftand scale barforband cat lowerright.
Contributionsin Science, Number 426 Barnes and Raschke: New MiocenePinniped 9
cranial material, and in light of the variety ofwal- feeding. The substrate could have been fine sedi-
rus-like pinnipeds now known to have existed in ments or even rocky surfaces, but in either case,
latest Miocene time, identification of these bones the prey items would have been benthic inverte-
remainstenuous.TheshaftoftheradiusofG. pug- brates. The closest living analogy to this type of
nax is nearly circular at midlength. Distally the food item would be the prey ofthe Recent walrus
radius expandsanteriorly,and on its lateralsurface (see Fay, 1982), although the method of feeding
it bears two deep ligamental grooves as is typical musthavebeendifferent.Livingwalruseshavehigh-
of Imagotariinae and Odobeninae (see Repenning ly vaulted palates, no anterior incisors, and verti-
and Tedford, 1977). callyorientedtusks.Theyfeedinrelativelyshallow
The ulna of G. pugnax is also stout, but it is water(beingtheshallowestdiversamongthe otari-
more slender than the ulna that was found asso- ids) by probing sandy or silty substrates with the
ciated with the radius (LACM 3011) from Santa sensitive muzzle and vibrissae, and eat mostly bi-
Cruz cited above. The olecranon process of the valved mollusks as well as a variety ofsoft-bodied
ulnais large, broad,and flaresposteriorly. Itsshape invertebrates such as tunicates, polychaete annelid
isveryunlikethenarrowerandmoreknoblikeolec- worms, priapulid worms, and sea cucumbers (Fay,
ranon processes on ulnae of typical fossil and Re- 1982).Thesoft-bodiedanimalsareingestedwhole.
cent odobenine walruses and of the ulna (LACM Walruses, however, do not chew up the shells of
3011) from Santa Cruz. The closest similarities to molluskstogetatthesoftparts.Theshellsareheld
G. pugnax among described fossil pinniped ulnae withthelargelips,andusingthetonguelikeapiston
are those that have been assigned to Imagotariinae within the highly vaulted mouth, the soft inner
(e.g., Repenning and Tedford, 1977:pl. 13, figs. 1, tissues are sucked out. The shells are mostly dis-
2). carded empty and nearly intact; they are not mas-
ticated by the cheek teeth and are not found in
DISCUSSION stomach contents (see Fay, 1982).
PALEOBIOLOGY Unlike walruses, however, G. pugnax does not
haveahighlyvaultedpalate,indicatingthatitprob-
The dentition of G. pugnax is very unusual for a ablywasunabletosuckoutthesoftpartsofshelled
pinniped,bothinitscompositionandinitsapparent mollusksusingitstongueasapiston.Theextensive
use during life. As in Recent walruses, the only breakage and wear of its teeth indicate either that
remaining incisors, upper or lower, are the P’s. In thefooditemswithhardpartswereingestedwhole
G. pugnax, the I3’s are large and procumbent, and chewed or that rocks were ingested with the
whereas, in the Recent walrus they are small, pre- food. It would seem that G. pugnaxprobably had
molariform,andhavemigratedtoapositionmedial a diet that included hard-shelled benthic inverte-
totheuppercanine(Fay, 1982). Nopinniped,fossil brates such as mollusks. Because the canine tusks
or living, has been described with large, procum- are very procumbent and are present in both the
bentuppertuskslikethoseofG. pugnax although upper and lower jaws, the angle of approach that
,
D. santacruzensis has smaller upper canines that G.pugnaxtooktothebottomandthewayitprobed
arenearlyasprocumbent.Nowalrus-likefossilhas the substrate must have been quite different from
been described with the lower canines developed that of walruses. Because the rostrum is shaped
as tusks also. Only D. santacruzensis shows any more like that ofa sea lion than a walrus, it prob-
tendencyforelongationofboththeupperandlow- ably did not have a broad muzzle with specialized
er canines (Repenning and Tedford, 1977); al- vibrissae such as modern walruses use to locate
though elongated, these remained caniniform and food.
certainlywould not be described as tusks (Kellogg, In life, G. pugnaxwas apparentlya huge, heavy-
1927; Mitchell, 1975). What remains of the cheek bodied pinniped, with a high forehead (at least in
teethofG.pugnaxindicatesthattheywerepeglike. the males, like the California sea lion, Z. califor-
Theircrowns are unknown, obliterated on the ho- nianus)andsmalleyes.Itprobablyhadaveryfleshy
lotype by random breakage in life and subsequent mouth, but no proboscis like an elephant seal and
massive wear. nobroadmuzzlelikeawalrus.Thelowerlipsmight
ClearlyG.pugnaxwasnoteatingfish,asdomost have been as large as the upper lips of living wal-
species of living otariids (King, 1983), which have ruses.Itslong,procumbentanteriorteethmusthave
normal-sized canines and pointed cheek teeth that projected outward from its mouth, there being no
do not normallyincursuch severewearand break- waythatitslipscouldhavecoveredthem.Thelarge
age. Gomphotariapugnax did not have large eyes, uppercanines curvedoutwardanddownwardwith
as do sea lions and seals and, therefore, probably the smallerpairofprocumbent I3’s between them.
did not dive to great depths in search offood. For Thelowercaninetuskscurvedupwardandoutward
this reason, and also because its teeth do not re- between the upper tusks.
semblethoseofthelivingelephantseals Mirounga The extensivepathologyofthe rightelbowjoint
(
spp.), it is also unlikely that it was a squid eater. indicates that the animal probably lived with its
Thewearontheupperandlowercanines,especially disabilityfora considerableperiodoftimepriorto
the anterior surfaces, indicates that these teeth its death at an extremely old age. The pathologic
probably contacted the ocean substrate during fusion of the joint may have inconvenienced the
10 Contributions in Science,Number426 Barnes and Raschke: New Miocene Pinniped